Axial-gap dynamo-electric machine
A stator for use in an axial-gap dynamo-electric machine. The stator core may be fabricated from a plurality of stator core elements each of which may be arranged to form teeth portions on a rotor side of the stator core elements and which also form back portions on a base side of the stator core elements. The stator core elements may contact one another such that magnetic, and other losses, are reduced and overall machine efficiency is improved over conventional designs.
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This application is based on, and claims priority to, Japanese Patent Application No. 2004-227065, filed Aug. 3, 2004, the entire contents of which are herein incorporated by reference.
BACKGROUNDApplications of interior permanent magnet synchronous motors (IPMSMs) in which permanent magnets are embedded in the rotors, and surface permanent magnet synchronous motors (SPMSMs) in which permanent magnets are glued to the rotor surfaces, are expanding to include electric vehicles and hybrid vehicles. These motor types offer distinct advantages because they are highly efficient and generate large output torques (their magnet torque and reluctance torque can be utilized).
Axial-gap motors, which are a type of permanent magnet synchronous motor having a stator and a rotor disposed facing each other in the axial direction, can be packaged in tight locations and thus they lend themselves to applications with layout constraints. An axial-gap motor is known as a type of dynamo-electric machine, for example, in which a single stator and two rotors maintain an air gap in the axial direction. (See Japanese patent application No. 2003-088032 for example.) A motorized two-wheeled vehicle having an axial-gap electric motor as its power source is also known. (See Japanese patent application No. 2003-191883 for example.)
BRIEF DESCRIPTION OF THE DRAWINGS
In the illustrated embodiment, rotation axle 1 is rotatably supported by both a first bearing 5 provided on the front side case 4a and a second bearing 6 provided on the rear side case 4b. Further, the rearward portion of rotation axle 1 may be joined to a rotation sensor 7 for sensing the rotation of axle 1.
Rotor 2 is secured to the rotation axle 1 and includes a rotor core 8 which may be made from laminated sheets of flat-rolled magnetic steel (ferromagnetic body) secured to rotation axle 1. Reactive forces are generated in permanent magnets 9 in reaction to the rotating magnetic flux provided by stator 3. These reactive forces cause rotor 2 to rotate about rotation axis 1′ of axle 1. Multiple permanent magnets 9 may be embedded in a surface of rotor 2 facing stator 3. Multiple permanent magnets 9 may be disposed such that adjacent surface magnetic polarities (North and South polarities) of permanent magnets 9 alternate. Rotor 2 is spaced from stator 3 such that air gap 10 is present and as a result, rotor 2 and stator 3 do not contact one another.
Stator 3 may be secured (e.g., fastened) to rear side case 4b and includes stator core 11 and a plurality of stator coils (exemplified at 12). Stator core 11 may be fabricated from a plurality of stator core elements 110 (e.g., see
As shown in
In contrast to the prior art design shown in
Because of the nature of the contact between the peripheral-direction end faces 110b′ and 110b′ of the ½ back portions 110b and 110b of adjacent stator core elements 110 and 110, an improved efficiency may be gained because the magnetic flux traverses the contact area between adjacent ½ back cores 110b and 110b as shown in
Furthermore, by eliminating the back core design of the prior art, the magnetic flux path of the prior art design (as measured from stator core to the back core and to an adjacent stator core) is shortened to form a magnetic path that traverses one stator core element 110 to another stator core element 110. Thus, among other things, the present invention reduces the number of junctions (from that of the conventional example) which in turn reduces magnetic flux loss (the embodiment of
By aligning the orientation of the laminations of the stator core elements 110 such as shown in
As explained above, the combined effect gained by expanding the magnetic flux path and by reducing the magnetic flux loss, both act to increase the magnetic flux density (i.e. the number of lines of magnetic flux oriented in the same direction per unit volume) of the electromagnet formed by stator core 11 and stator coils 12. This multiplied effect results in improved machine efficiency.
By constructing each stator core element 110 as an integrated T-shape element, magnetic flux loss is reduced by reducing the number of junctions compared to the conventional example. In addition, eliminating the conventional back core, reduces the number of components leading to cost reduction. Also, because stator core elements may be fabricated from steel plates which are laminated together and oriented parallel to rotation axis 1′, magnetic flux loss (resulting from components which do not have aligned laminated sheets) and the consequent generation of undesirable loop currents, are both eliminated.
In the embodiment of
Because stator core element 110 can be configured in a U-shape which includes a pair of ½ teeth members 110a and 110a integrated with a back portion 110b, and also because adjacent U-shaped stator core elements 110 are disposed such that the peripheral-direction end faces 110a′ and 110a′ of the ½ teeth cores 110a and 110a of adjacent stator core elements 110 and 110 may contact each other, the lines of magnetic flux do not cross one another and thus, a loss of magnetic flux is minimized. Additionally, eliminating the conventional back core design reduces the number of components leading to cost reduction.
A donut-shaped stator-securing cover 15 may be provided in which a plurality of through-holes 15a may be formed in locations corresponding with teeth portions 110a of stator core elements 110. Through-holes 15a are formed in the stator-securing cover 15 such that securing-cover 15 is easily manipulated along axis 1′ from the rotor side of stator core 11 into registration with, and to engage, the plurality of tooth portions 110a of stator core 11. Because the remainder of the configuration shown in
In the embodiment of
Because of the relatively broad base of contact between the back portion of stator core element 110 and plate 14, and also because of the positive engagement between positioning projections 110c and positioning grooves 14a, stator core 11 is prevented from moving relative to position plate 14. Moreover, the engagement between positioning projections 110c and positioning grooves 14a ensures positive alignment between peripheral-direction end faces 110b′ of adjacent stator core elements 110. Furthermore, installing stator securing cover 15 over teeth portions 110a defines the radial position of each stator core element 110 and the axial-direction secureness of each stator core element 110 is established. Also, the planar accuracy of the rotor-facing surface 110d of each stator core element 110 is achieved in the axial-direction. As a result, it is easier to control the size of air gap 10 between the stator-facing surface of permanent magnet 9 of the rotor and the rotor-facing surface 110d of the stator core elements 110. Additionally, the use of stator-securing cover 15 allows the air gap 10 size to be adjusted to achieve maximum machine efficiency.
The embodiments described herein set forth applications in which a single rotor and a single stator are used. However, any number of rotor-stator combinations may be used, including a single rotor and two stators, two rotors and a single stator, two rotors and three stators, three rotors and two stators, or the like. Additionally,
Although the back portion of the stator core elements 110 can be defined by symmetrical fractional sub-portions, (e.g., a pair of ½ back portions, 110b and 110b), one skilled in the art will recognize that the back portion can be defined by non-symmetrical fractional sub-portions (e.g., ⅓ and ⅔ portions) and also that back portion can be defined such that no fractional sub-portions exist (e.g., 100% and 0%). Additionally, although the fractional tooth portions 110a and 110a have been illustrated herein as symmetrical ½ tooth portions, one skilled in the art will recognize that tooth portions 110a and 110a can be defined by non-symmetrical fractional sub-portions (e.g., ⅓ and ⅔) without deviating from the spirit of the invention.
The present invention has been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best modes known for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.
Claims
1. An axial-gap dynamo-electric machine including a rotor on which permanent magnets are disposed and a stator having a stator core, wherein said rotor and said stator core are disposed along a common axis, wherein said rotor is rotatably supported providing an air gap between the rotor and the stator, wherein the stator core, comprises:
- a plurality of stator core elements, wherein each stator core element includes a tooth portion disposed on a rotor side of the stator core element and a back portion disposed on a base side of the stator core element, wherein the tooth portion is integrally formed with the back portion, wherein the stator core elements are disposed adjacent to one another such that the back portions of adjacent stator core elements contact one another, and wherein the back portions of the stator core elements are secured to a dynamo-electric machine case.
2. The axial-gap dynamo-electric machine of claim 1, wherein the back portion of each stator core element includes a pair of ½ back portions, wherein the tooth portion and the pair of ½ back portions integrally form a generally T-shaped cross-section, wherein each ½ back portion in the pair of ½ back portions includes a peripheral-direction end face, and wherein adjacently disposed stator core elements contact one another along their peripheral-direction end faces.
3. The axial-gap dynamo-electric machine of claim 1, wherein the tooth portion of each stator core element includes a pair of ½ teeth portions, wherein the back portion and the pair of ½ teeth portions integrally form a generally U-shaped cross-section, wherein each ½ tooth portion in the pair of ½ teeth portions includes a peripheral-direction end face, and wherein adjacently disposed stator core elements contact one another along their peripheral direction end faces.
4. The axial-gap dynamo-electric machine of claim 1, further including,
- a position plate, for mounting to the plurality of stator core elements, wherein radial-direction, convex structures are disposed on the back portion of each stator core element, wherein said position plate includes radial-direction, concave structures that engage the radial-direction, convex structures on the back portion of each stator core element, and wherein said position plate is secured to said dynamo-electric machine case.
5. The axial-gap dynamo-electric machine of claim 1, further including,
- a donut-shaped stator-securing cover having through-holes formed therein, wherein said through-holes register with corresponding teeth portions of the stator core elements of the stator core, wherein said donut-shaped stator securing cover snappingly engages the rotor side of the stator core elements.
6. The axial-gap dynamo-electric machine of claim 1, wherein each stator core element is formed from a plurality of steel plates laminated together such that the steel plates are generally perpendicular to a radial line originating from an axis of rotation of said axial-gap dynamo-electric machine.
7. The stator of claim 1, further including,
- a position plate for mounting to the plurality of stator core elements,
- means for fastening each stator core element to said position plate.
8. A stator for use in an axial-gap dynamo-electric machine, comprising:
- a plurality of stator core elements, wherein each stator core element includes a tooth portion and a back portion, and wherein the stator core elements are disposed adjacent to one another such that the back portions of adjacent stator core elements contact one another.
9. The stator of claim 8, wherein the tooth portion is integral with the back portion to form a generally T-shaped cross-section, wherein each back portion includes a first and a second peripheral-direction end face, and wherein adjacently disposed stator core elements contact one another along their peripheral-direction end faces.
10. The stator of claim 8, wherein the tooth portion of each stator core element includes a pair of teeth, wherein the back portion is integral with the pair of teeth to form a generally U-shaped cross-section, wherein each tooth in each pair of teeth includes a peripheral-direction end face, and wherein adjacently disposed stator core elements contact one another along their peripheral direction end faces.
11. The stator of claim 8, further including,
- a position plate for mounting to the plurality of stator core elements, wherein each stator core element includes at least one of a depression or a projection that engages a mating structure formed in the position plate.
12. The stator of claim 11, wherein the at least one depression or projection of each stator core element is elongated along a radial-direction defined by a radial line extending from an axis of rotation associated with said stator.
13. The stator of claim 11, wherein each stator core element is formed from a plurality of steel plate laminations.
14. The stator of claim 13, wherein the plurality of stator core elements are fastened to said position plate such that the steel plate laminations of each sector core element are generally perpendicular to a radial line extending from an axis of rotation associated with the stator.
15. The stator of claim 11, wherein the at least one depression or projection in each stator core element snappingly engages the mating structure formed in the position plate.
16. The stator of claim 8, further including,
- a stator-securing element having engagement openings adapted to mate with the tooth portions of each stator core element.
17. The stator of claim 16, wherein the engagement openings of the stator-securing element are sized relative to the tooth portions of each stator core element such that the engagement openings snappingly mate with the tooth portions.
18. The stator of claim 8, further including,
- a position plate for mounting to the plurality of stator core elements,
- means for fastening each stator core element to said position plate.
Type: Application
Filed: Jul 29, 2005
Publication Date: Feb 9, 2006
Applicant: Nissan Motor Company, Ltd. (Kanagawa)
Inventors: Yuusuke Minagawa (Kanagawa), Noriyuki Ozaki (Yokohama-shi)
Application Number: 11/192,557
International Classification: H02K 21/12 (20060101); H02K 1/00 (20060101); H02K 1/22 (20060101);